Structural highlights
Disease
[MITF_MOUSE] Defects in Mitf are the cause of microphthalmia (mi), a condition characterized by loss of pigmentation; reduced eye size; failure of secondary bone resorption; reduced numbers of mast cells; early onset of deafness, and which gives rise to a number of different phenotypes. Among them, microphthalmia-eyeless white (mi-ew) has a normal appearance at the heterozygous state, but shows white coat; eyes almost absent and eyelids never open at homozygosity. Microphthalmia-black and white spot (mi-bws) is normal at heterozygosity, and presents white spots and black eyes at homozygous state. Microphthalmia-white (mi-wh) has reduced coat color and eye pigmentation; spots on toes, tail and belly; inner ear defects at heterozygosity, and at homozygosity shows white coat; eyes small and inner iris slightly pigmented; spinal ganglia, adrenal medulla and dermis smaller than normal, and inner ear defects. Microphthalmia-vitiligo (mi-vi) has normal phenotype at heterozygosity, but shows gradual depigmentation of coat, skin and eyes; and retinal degeneration at homozygosity. Microphthalmia-spotted (mi-sp) shows normal phenotype; at homozygosity, however, tyrosinase activity in skin is reduced. Microphthalmia-defective irism (mi-di) has reduced retinal pigmentation at heterozygosity and shows white coat; eyes of reduced sized and possible mild osteoporosis at homozygosity. Microphthalmia-cloudy eyed (mi-ce) has a normal appearance at the heterozygous state, but shows white coat; eyes of reduced size and unpigmented at homozygosity. Microphthalmia-red-eyed white (mi-rw) has a normal appearance at the homozygous state, but shows white coat with one or more pigmented spots around the head/and or tail; eyes are small and red at heterozygosity. Microphthalmia-black-eyed white (mi-bw) shows a white coat but normal sized eyes which reamin black at homozygosity.
Function
[MITF_MOUSE] Transcription factor that regulates the expression of genes with essential roles in cell differentiation, proliferation and survival. Binds to symmetrical DNA sequences (E-boxes) (5'-CACGTG-3') found in the promoters of target genes, such as BCL2 and tyrosinase (TYR). Plays an important role in melanocyte development by regulating the expression of tyrosinase (TYR) and tyrosinase-related protein 1 (TYRP1). Plays a critical role in the differentiation of various cell types, such as neural crest-derived melanocytes, mast cells, osteoclasts and optic cup-derived retinal pigment epithelium.
Publication Abstract from PubMed
Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and an important oncogene in melanoma. MITF heterodimeric assembly with related basic helix-loop-helix leucine zipper transcription factors is highly restricted, and its binding profile to cognate DNA sequences is distinct. Here, we determined the crystal structure of MITF in its apo conformation and in the presence of two related DNA response elements, the E-box and M-box. In addition, we investigated mouse and human Mitf mutations to dissect the functional significance of structural features. Owing to an unusual three-residue shift in the leucine zipper register, the MITF homodimer shows a marked kink in one of the two zipper helices to allow an out-of-register assembly. Removal of this insertion relieves restricted heterodimerization by MITF and permits assembly with the transcription factor MAX. Binding of MITF to the M-box motif is mediated by an unusual nonpolar interaction by Ile212, a residue that is mutated in mice and humans with Waardenburg syndrome. As several related transcription factors have low affinity for the M-box sequence, our analysis unravels how these proteins discriminate between similar target sequences. Our data provide a rational basis for targeting MITF in the treatment of important hereditary diseases and cancer.
Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF.,Pogenberg V, Ogmundsdottir MH, Bergsteinsdottir K, Schepsky A, Phung B, Deineko V, Milewski M, Steingrimsson E, Wilmanns M Genes Dev. 2012 Dec 1;26(23):2647-58. doi: 10.1101/gad.198192.112. PMID:23207919[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Pogenberg V, Ogmundsdottir MH, Bergsteinsdottir K, Schepsky A, Phung B, Deineko V, Milewski M, Steingrimsson E, Wilmanns M. Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF. Genes Dev. 2012 Dec 1;26(23):2647-58. doi: 10.1101/gad.198192.112. PMID:23207919 doi:http://dx.doi.org/10.1101/gad.198192.112
